Conventionally, in a construction using steel-pipe columns, there are parts that connect columns in the vertical direction. For such connection parts, the sizes of the columns to be connected in the vertical direction may differ. An example is a case in which the size of an upper column is smaller than that of the lower column. In such cases, there is a method in which a taper shaped connecting member is used between columns to be connected.
However, manufacturing such a taper shaped member is difficult. In addition, since the taper shaped member meets obliquely with the upper and lower horizontal surfaces connected thereof, an edge surface of a backing metal, which is a plate-like member provided at the connection part between the taper shaped member and the horizontal surface, is not in surface contact but in line contact with the horizontal surface. Therefore, welding at this part becomes difficult and may cause welding defects.
On the other hand, columns that are to be connected vertically may not always be arranged coaxially. For example, a column is classified either as a center column, a side column, or a corner column according to the position of the column in the construction, and the connection position of the upper and lower columns is different in each of the column structures. And, if the connection positions of columns are different in this way, the strength required for the connecting member for columns differs depending on the connection position of the column. However, thickening the whole body so to be adaptable to every case may result in increase in weight and cost. Therefore, it is necessary to reinforce each part with an appropriate shape.
As such a connection structure of columns, there is a connecting member for columns that has marks showing each of the connection positions for a center column, a side column, and a corner column (Patent Document 1).